Quasar

Artist's rendering of the accretion disc in ULAS J1120+0641, a very distant quasar powered by a supermassive black hole with a mass two billion times that of the Sun[1]
The Chandra X-ray image is of the quasar PKS 1127-145, a highly luminous source of X-rays and visible light about 10 billion light-years from Earth. An enormous X-ray jet extends at least a million light-years from the quasar. Image is 60 arcseconds on a side. RA 11h 30m 7.10s Dec −14° 49' 27" in Crater. Observation date: May 28, 2000. Instrument: ACIS

A quasar (/ˈkwzɑːr/ KWAY-zar) is an extremely luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by a supermassive black hole with a mass ranging from millions to tens of billions of solar masses, surrounded by a gaseous accretion disc. Gas in the disc falling towards the black hole heats up and releases energy in the form of electromagnetic radiation. The radiant energy of quasars is enormous; the most powerful quasars have luminosities thousands of times greater than that of a galaxy such as the Milky Way.[2][3] Quasars are usually categorized as a subclass of the more general category of AGN. The redshifts of quasars are of cosmological origin.[4]

The term quasar originated as a contraction of "quasi-stellar [star-like] radio source"—because they were first identified during the 1950s as sources of radio-wave emission of unknown physical origin—and when identified in photographic images at visible wavelengths, they resembled faint, star-like points of light. High-resolution images of quasars, particularly from the Hubble Space Telescope, have shown that quasars occur in the centers of galaxies, and that some host galaxies are strongly interacting or merging galaxies.[5] As with other categories of AGN, the observed properties of a quasar depend on many factors, including the mass of the black hole, the rate of gas accretion, the orientation of the accretion disc relative to the observer, the presence or absence of a jet, and the degree of obscuration by gas and dust within the host galaxy.

About a million quasars have been identified with reliable spectroscopic redshifts,[6] and between 2-3 million identified in photometric catalogs.[7][8] The nearest known quasar is about 600 million light-years from Earth. The record for the most distant known quasar continues to change. In 2017, quasar ULAS J1342+0928 was detected at redshift z = 7.54. Light observed from this 800-million-solar-mass quasar was emitted when the universe was only 690 million years old.[9][10][11] In 2020, quasar Pōniuāʻena was detected from a time only 700 million years after the Big Bang, and with an estimated mass of 1.5 billion times the mass of the Sun.[12][13] In early 2021, the quasar QSO J0313–1806, with a 1.6-billion-solar-mass black hole, was reported at z = 7.64, 670 million years after the Big Bang.[14]

Quasar discovery surveys have shown that quasar activity was more common in the distant past; the peak epoch was approximately 10 billion years ago.[15] Concentrations of multiple quasars are known as large quasar groups and may constitute some of the largest known structures in the universe if the observed groups are good tracers of mass distribution.

  1. ^ "Most Distant Quasar Found". ESO Science Release. Retrieved 4 July 2011.
  2. ^ Wu, Xue-Bing; et al. (2015). "An ultraluminous quasar with a twelve-billion-solar-mass black hole at redshift 6.30". Nature. 518 (7540): 512–515. arXiv:1502.07418. Bibcode:2015Natur.518..512W. doi:10.1038/nature14241. PMID 25719667. S2CID 4455954.
  3. ^ Frank, Juhan; King, Andrew; Raine, Derek J. (February 2002). Accretion Power in Astrophysics (Third ed.). Cambridge, UK: Cambridge University Press. Bibcode:2002apa..book.....F. ISBN 0521620538.
  4. ^ "Quasars and Active Galactic Nuclei". ned.ipac.caltech.edu. Retrieved 2020-08-31.
  5. ^ Bahcall, J. N.; et al. (1997). "Hubble Space Telescope Images of a Sample of 20 Nearby Luminous Quasars". The Astrophysical Journal. 479 (2): 642–658. arXiv:astro-ph/9611163. Bibcode:1997ApJ...479..642B. doi:10.1086/303926. S2CID 15318893.
  6. ^ "Million Quasars Catalog, Version 8 (2 August 2023)". MILLIQUAS. 2023-08-02. Retrieved 2023-11-20.
  7. ^ Shu, Yiping; Koposov, Sergey E; Evans, N Wyn; Belokurov, Vasily; McMahon, Richard G; Auger, Matthew W; Lemon, Cameron A (2019-09-05). "Catalogues of active galactic nuclei from Gaia and unWISE data". Monthly Notices of the Royal Astronomical Society. 489 (4). Oxford University Press (OUP): 4741–4759. arXiv:1909.02010. doi:10.1093/mnras/stz2487. ISSN 0035-8711.
  8. ^ Storey-Fisher, Kate; Hogg, David W.; Rix, Hans-Walter; Eilers, Anna-Christina; Fabbian, Giulio; Blanton, Michael; Alonso, David (2024). "Quaia, the Gaia-unWISE Quasar Catalog: An All-Sky Spectroscopic Quasar Sample". AAS Journals. 964 (1): 69. arXiv:2306.17749. Bibcode:2024ApJ...964...69S. doi:10.3847/1538-4357/ad1328.
  9. ^ Bañados, Eduardo; et al. (2018). "An 800-million-solar-mass black hole in a significantly neutral Universe at a redshift of 7.5". Nature. 553 (7689): 473–476. arXiv:1712.01860. Bibcode:2018Natur.553..473B. doi:10.1038/nature25180. ISSN 0028-0836. PMID 29211709. S2CID 205263326.
  10. ^ Choi, Charles Q. (6 December 2017). "Oldest Monster Black Hole Ever Found Is 800 Million Times More Massive Than the Sun". Space.com. Retrieved 6 December 2017.
  11. ^ Landau, Elizabeth; Bañados, Eduardo (6 December 2017). "Found: Most Distant Black Hole". NASA. Retrieved 6 December 2017.
  12. ^ "Monster Black Hole Found in the Early Universe". Gemini Observatory. 2020-06-24. Retrieved 2020-08-31.
  13. ^ Yang, Jinyi; Wang, Feige; Fan, Xiaohui; Hennawi, Joseph F.; Davies, Frederick B.; Yue, Minghao; Banados, Eduardo; Wu, Xue-Bing; Venemans, Bram; Barth, Aaron J.; Bian, Fuyan (2020-07-01). "Poniua'ena: A Luminous z = 7.5 Quasar Hosting a 1.5 Billion Solar Mass Black Hole". The Astrophysical Journal Letters. 897 (1): L14. arXiv:2006.13452. Bibcode:2020ApJ...897L..14Y. doi:10.3847/2041-8213/ab9c26. S2CID 220042206.
  14. ^ Temming, Maria (January 18, 2021). "The most ancient supermassive black hole is bafflingly big". Science News..
  15. ^ Schmidt, Maarten; Schneider, Donald; Gunn, James (1995). "Spectroscopic CCD Surveys for Quasars at Large Redshift. IV. Evolution of the Luminosity Function from Quasars Detected by Their Lyman-Alpha Emission". The Astronomical Journal. 110: 68. Bibcode:1995AJ....110...68S. doi:10.1086/117497.

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